Alloy for use in spark plug electrodes and the like



Patented Dec. 16," 1941 UNITED STATES 2,266,318 PATIENT OFFICE ALLOYFOR- USE IN SPARK PLUG ELECTRODES AND THE LIKE Walter F. Heller, Flint,ma. assignor to General Motors Corporation, Detroit, Mich, a corporationof Delaware No Drawing. Application August 23, 1940, Serial N0. 353,842

'9 Claims. (Cl. 123-169) This invention has to do with an improvedalloy'resistant to heat and corrosion especially produce rapiddeterioration of most alloys ordi- 1o narily regarded as resistant toheat and corrosion.

An electrode alloy. that has been found to be particularly useful forthis service is disclosed in Randolph Patent No. 2,001,888 granted May21,

1935. This alloy consists essentially of nickel and chromium togetherwith a small proportion of .barium. In addition to durability andrelatively good heat conductivity, this alloy possesses the advantage oflowering the sparking voltage owing tothe quantity of low work functionmaterial-in this instance barium-contained in it. In its inclusion oflow work function material the Randolph alloy constitutes an embodimentof "the invention described and claimed in Patent No. 1,872,065 issuedto Rabezzana and Duffendack on August 16, 1932.

I have succeeded in substantially improving the alloy of the Randolphpatent as well as similar alloys in which barium is omitted by theaddition of a small proportion of columbium, pref e'rably on the orderof from .1 to- 10%. The columbium greatly increases resistance tocorrosion and wear and together with the other additions hereinafterdescribed improves the life and performance of the electrodes. Thefollowing is the alloy composition at present preferred for production:

Per cent Chromium 3.5 0 Barium .02 Columbium 1.5 Iron 1.0 Manganese 1.0Silicon 1.0 Magnesium A trace Nickel Balance Alloys of 'markedsuperiority have also been employed having compositions fallingwithinthe following range:

- Per cent Chromium .5 to 15 Barium 0to .3 columbium .1 to 10 5Manganese Q 0 to 6 Iron 0 to 10 Silicon 0 to 5 Magnesium A trace NickelBalance 6 The high temper- 5 i I tion of this material is increased.

The improved alloy is subject to considerable modification in practice.If lowered sparking voltage is not desired, barium'may be omitted. Theuse of other alkaline earth metals such as calcium and strontium toreplace barium in whole or in part is indicated as these likewisepossess low work function and tend to reduce the sparking voltage.

It will usually be found tobe desirable to use smaller amounts ofcolumbium because of the high cost of this material although improvementin corrosion resistance increasesas the proporvenient and mosteconomical way to add columbium is in the form of a ferro-columbiumalloy,

hence the iron content of my improved alloy..

Manganese is employed as a deoxidizer to prevent intercrystallinecorrosion and increase the workability of the material. Other knowndeoxidizers may be employed for the same purpose.

Silicon is introduced for the purpose of further increasing resistanceto wear and corrosion. It may be omitted if desired.

The trace of magnesium is the residue of a small amount, usually about.1%, added to facilitate drawing.

Cobalt is indicated as a substitute in whole or in part for nickel butnickel base alloys have proven much more corrosion-resistant.

The alloy is preferably prepared in substantially the same way as thealloy of the Randolph patent, that is, all of the materials exceptbarium are melted together and then barium, preferably wrapped in nickelfoil to exclude air, is introduced beneath the surface of the melt,followed by casting in ingots and drawing to shape.

Electrodes made of the new composition have I proven on many exhaustivetests in severe service to have exceptionally long life'and to give'unusually satsifactory performance. Inasmuch as electrode life is animportant factor limiting spark plug performance especially in the caseof high quality plugs such as are used in modern airplane engines, themarked improvement obtainable with the alloy here disclosed is of greatpractical value.

While both the center and side electrodes may be made of'the new alloy Ihave found it best to use the new alloy only for the side electrode andthe lower part of the center electrode, em-

ploying for the' balance of the center electrode material, such ascopper, possessing better, heat conductivity. If preferred the upperpart of the electrode may be encased in a sheathof the new alloy forminga continuation of the lower part of the electrode so as to protect itfrom the cor- .rosive action of combustion chamber gases. It

is important in spark plugdesign that the center electrode be wellsealed in the insulator so as to I prevent loss of compression. Suchsealing also.

The most conprevents the combustion gases from attacking the upperportion of the electrode.

I claim: Y

1. A spark plug having an electrode made of an alloy having as its majorconstituent a metal of the group consisting of nickel and cobalt,together with chromium and columbium to improve the resistance tocorrosion.

2. A spark plug having an electrode made of an alloy having as its majorconstituent a metal of the group consisting of nickel and cobalt,toather with chromium and columbium to improve the resistance tocorrosion, and a small proportion of a material of low work function toreduce the sparking voltage.

. 3. An electrode for spark plugs and the like made of an alloy ofnickel, chromium and columbium together with a small proportion ofbarium to reduce the sparking voltage.

4. An electrode for spark plugs and the like made of an alloy consistingsubstantially of from .5 to 15% chromium, 0 to 3% barium, .1 to 10%columbium, 0 to 6% of a suitable deoikidizer such as manganese, 0 to 10%iron, 0 to 5% silicon, and the balance nickel.

5. An electrode for spark plugs and the like made of an alloy consistingsubstantially of from .5 to 15% chromium from .01 to .3% barium, from .1to 10% columbium, and the balance nickel. I

6. An electrode for spark plugs and the like made of an alloy consistingof approximately 3.5% chromium, .02 barium, 1.5% columbium,

1.0% iron, 1% manganese, 1% silicon and the balance nickel.

7. A heat and corrosion-resistant alloy consisting substantially of from.5 to 15% chromium, 0 to .3% barium, .1 to 10% columbium, 0 to 6% of asuitable deoxidizer such as manganese, 0 to 10% iron, 0 to 5% silicon,and the balance nickel.

8. A heat and corrosion-resistant alloy consisting substantially of from.5 to 15% chromium, from .01 to .3% barium, from .1 to 10% columbium,and the balance nickel.

9. A heat and corrosion-resistant alloy consisting of approximately 3.5%chromium, .02% barium, 1.5% columbium, 1.0% iron, 1% manganese, 1%silicon and the balance nickel.

WALTER F. HELLER.

